Polyhedral oligomeric silsesquioxane (POSS) cage molecules and polyhedral oligomeric silicate (POS) (spherosilicate) cage molecules or reagents are increasingly being utilized as building blocks for the preparation of novel catalytic materials and as performance enhancement additives for commodity and engineering polymers. The physical sizes and structures of POSS and POS reagents are on the nanometer dimension (10.sup.-9 m) and they can be described as the smallest "silica-like" particles possible. Their nanometer size and unique hybrid (inorganic-organic) chemical composition are responsible for the many desirable property enhancements which have been observed upon incorporation of POSS/POS reagents into polymer systems. The most attractive POSS building blocks for the synthesis of linear polymer systems are POSS reagents that posses only one or two reactive chemical functionalities. When incorporated into a polymerization reaction these reagents provide high yields of linear polymers which are essentially free from impurities and have controllable properties through the appropriate selection of synthesis processes and/or starting materials. Conversely, the most attractive POSS building blocks for the synthesis of network polymers and/or use in sol-gel processes are POSS reagents which have been appropriately funtionalized with groups containing three or more reactive functionalities.
Three primary synthetic routes to functionalized POSS and POS based cage reagents have been reported. These have involved the following: (1) Polycondensation of trifunctional RSiY.sub.3 precursors where R=a hydrocarbon and Y is a hydrolizable functionality such as chloride, an alkoxide or silanol. (2) Functionalization of fully substituted silane compounds such as via hydrosilylation or chlorination chemistry. Similarly, silylation of anionic species has been reported to produce functionalized species. Wiedner, et al U.S. Pat. No. 5,047,492, teach the production of exhaustively functionalized polyhedral oligomeric silsesquioxanes through processes involving either the addition of hydrogen atoms bonded directly to silicon atoms onto aliphaticly unsaturated compounds or the addition of sulfur atoms onto aliphaticly unsaturated compounds. Laine et al, Macromolecules, (1996), v. 29:2327-2330, also teach the addition of hydrogen atoms bonded directly to silicon atoms onto aliphaticly unsaturated compounds to produce polyfunctional silsesquioxanes.
Without exception, all of the reported methods have limited utility because they suffer from one or more of the following draw backs. (1) The synthetic route does not afford significant stereochemical control over the placement of the functionality on the cage species. (2) The method does not afford control over the degree of substitution that can take place and results in the formation of isomeric mixtures. (3) The type of organic functionality that can be incorporated on the cage is limited because the methods are intolerant to a broad range of chemical functionalities. (4) The methods do not afford a high yield route to the desired product, which results in the formation of impurities arising from side reactions that must be subsequently removed. (5) The functionalities are limited to the addition of hydrogen atoms bonded directly to heteroatoms (i.e. silicon or sulfur).
In the prior art is a reference to preparation of POSS monomers and synthesis of polymers therefrom, U.S. Pat. No. 5,484,867 to J. D. Lichtenhan et al (1996), which reference, however, is not believed to suggest the present invention.
Accordingly, there is need and market for improved functionalization of polycyclic silicones that overcomes the above prior art shortcomings.
There has now been developed, per the invention, efficient methods for the selective functionalization of the above polyfunctional species using the novel process steps discussed below.